The present invention relates to a downhole packer for use in a well bore. More particularly, the present invention relates to a packer which can be used for downhole testing.
During well completions it is desirable to check the integrity of the production bore and any packers used to isolate portions of the well. A known technique for this is to perform an inflow or negative test. One or more packers are inserted into the well bore to seal off a portion of the well. Low density fluid is introduced to the work string reducing hydrostatic pressure within the pipe. As a consequence of the drop in hydrostatic pressure, well bore fluid flows through any cracks or irregularities into the bore resulting in an increase in pressure which can be monitored and used to indicate where repairs are necessary.
Typically, a separate trip is required to be made into the well to perform an inflow or negative pressure test. This is because the conventional packer tools used are set by a relative rotation within the well bore. As many other tools are activated by rotation it is likely that the packer would prematurely set. This problem has been overcome by the introduction of a weight set packer. Such a weight set packer, referred to as a compression set packer, is disclosed in the Applicant's International Patent Application, publication no. WO/0183938. The packer is set by a sleeve moveable on a body of the packer being set down on a formation in the well bore. Movement of the sleeve compresses one or more packing elements to provide a seal.
This compression set packer is particularly suitable for integrity testing of a completion when a permanent packer, or ‘tieback’ packer, with a Polished Bore Receptacle (PBR) has been used. Once the permanent packer with the PBR has been set, a single trip can be made into the well to operate clean-up tools and perform an in-flow or negative test. The clean-up tools may be operated by relative rotation of the work string in the well-bore and further the work string can be slackened off so that the sleeve of the compression set packer lands out on the PBR. This sets the compression set packer above the PBR and seals the bore between the packers. An in-flow or negative test can then be performed.
A significant disadvantage of this compression set packer is that if the sleeve contacts a surface prior to reaching the PBR, the packer can be prematurely set. Additionally, as the work string requires to move through the bore relative to the sleeve for compression to occur, the compression set packer cannot be run on the same string as the tieback packer and PBR.
It is an object of the present invention to provide a compression set packer which includes a mechanism to prevent premature setting of the packer in a well bore.
It is a further object of at least one embodiment of the present invention to provide a packer which can be run with a tubular in a well bore to seal above the tubular when the tubular is positioned in the well bore.
It is a further object of at least one embodiment of the present invention to provide a method of performing an in-flow test in a well bore on the same trip as setting a tieback packer including a polished bore receptacle.